The present invention relates to a suspension system, and more particularly to a semi-independent suspension system for a mass transit vehicle which provides a significantly lower floor profile.
Mass transit vehicles, such as trolley cars, buses, and the like typically have seats aligned at the lateral sides of the vehicle, with a central aisle and floor extending along the vehicle. In order to facilitate entering and exiting from the vehicle, it is desirable to have the vehicle floor and aisle positioned relatively low to the ground. This provides faster cycle time if the bus stops and more comfort to passengers.
Mass transit vehicles typically have several axles which support, drive and steer the vehicle. Many such vehicles provide a rigid axle having a gear box at a longitudinal end to form an inverted portal axle configuration. Disadvantageously, this arrangement has limited ride benefits resultant from the rigid axle suspension system.
In other known embodiments, relatively more complex independent suspension systems have been available with either a single reduction carrier on relatively lighter vehicles or a double reduction system on relatively heavier vehicles. The reduction carriers are located near the axle centerline and thus take up a significant amount of packaging space. As these components are aligned near the longitudinal axis of the vehicle, the floor profile must be raised for a significant length of the vehicle. Raising the floor profile in such a manner requires the passengers to climb up to a platform above the axle, which renders that portion of the bus either inaccessible or uncomfortable.
Accordingly, it is desirable to provide a suspension system which provides ride benefits associated with independent suspension systems while maintaining a low floor profile to improve access to the vehicle.
The suspension system according to the present invention provides a first and second set of hub assemblies which are each mounted to an independent swing-arm. The swing arm pivots about a pivot axis. The pivot axis is located below (closer to the ground than) a rotational axis defined by the hub assemblies.
A hub gear box is operably connected to each hub assembly to provide torque to drive their respective set of wheels. An input gear box drives one hub gear box. The input gear box defines an input axis substantially offset from the rotational axis. A coupling extends from one input gear box to receive an input driveline from a drive source such as vehicle engine. The coupling is located proximate the pivot axis to minimize relative movement during articulation of the swing arm. That is, as the pivot axis is closer to the input gear box coupling, motion of the coupling is less than that of the hub gear box and hub assemblies during articulation.
An axle housing extends from the input gear box to an opposite hub gear box. The axle housing transmits power from the input gear box to the opposite hub gear box. The axle housing further serves as a torsion bar between the swing arms and to minimize additional support structure.
The present invention therefore provides ride benefits associated with independent suspension systems while maintaining a low floor profile to improve access to the vehicle.